Most domestic espresso makers lack an effective way to measure the delivered dosage of brewed coffee. Some machines monitor the flow volume with flow sensors that measure the volume of water pumped into the thermal block or boiler. Operating in this way assumes that the volume pumped into the thermal block or boiler is equal to the volume delivered out of the portafilter into the user's cup. However, this assumption does not always hold. This is because some of the water delivered into the boiler or thermal block ends up as residue or is captured by absorption or other losses taking place in the filter, thermal block or boiler. While it would be more accurate to measure the flow out of the boiler or thermal block, low cost flow sensors are not considered suitable because they are adversely affected by the higher temperatures and contamination associated with the liquid delivery system downstream of the thermal block or boiler.